Environmental activists have invited some of the UK's leading architects to design an "impenetrable fortress" to be built on land earmarked for the third runway at Heathrow.
Greenpeace plans to build the winning design at the centre of the site where airport operator BAA hopes to construct a £7bn runway and a sixth terminal.
The charity bought the parcel of land last year and then distributed ownership to more than 60,000 supporters around the world.
Organisers say the small individual plots will create a legal headache for any government trying to push ahead with the expansion plans.
